• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.115-116
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• 2023

This study aims to investigate and improve the carbon dioxide sequestration capability and the mechanical properties of non-hydraulic low calcium silicate cement especially designed for CO₂ reaction and ordinary Portland cement subjected to the carbonation curing facilitating pH swing method. Nitric acid (HNO₃) was utilized as an liquid for the mixing of cement paste to enhance the initial dissolution of Ca ions from the cements by promoting low pH environment and prevent the direct precipitation of Ca with the anion, owing to the high solubility of Ca(NO₃)₂ in water. The results presented that the higher the concentration of HNO₃, the higher the compressive strength and CO₂ sequestration (until 0.1 M). Ca dissolution caused by the harsh acid attack onto the anhydrous cement particle lead to the higher carbonation reaction degree, forming abundant CaCO₃ crystals after the reaction. However, cement paste mixed with excessively high concentration of HNO₃ presented deterioration due to the too harsh pH environment and abundant NO₃- ions which are known to retard the reaction of cement.

• Journal of Electrochemical Science and Technology
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• v.7 no.2
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• pp.91-96
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• 2016

Oxidation behaviours of ash free coal (AFC), carbon, and H₂ fuels were investigated with a coin type molten carbonate fuel cell. Because AFC has no electrical conductivity, its oxidation occurs via gasification to H₂ and CO. An interesting behaviour of mass transfer resistance reduction at higher current density was observed. Since the anode reaction has the positive reaction order of H₂, CO₂ and H₂O, the lack of CO₂ and H₂O from AFC results in a significant mass transfer resistance. However, the anode products of CO₂ and H₂O at higher current densities raise their partial pressure and mitigate the resistance. The addition of CO₂ to AFC reduced the resistance sufficiently, thus the resistance reduction at higher current densities did not appear. Electrochemical impedance results also indicate that the addition of CO₂ reduces mass transfer resistance. Carbon and H₂ fuels without CO₂ and H₂O also show similar behaviour to AFC: mass transfer resistance is diminished by raising current density and adding CO₂.

• Korean Journal of Environmental Agriculture
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• v.42 no.3
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• pp.231-238
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• 2023

We analyzed the variations in the CO₂ concentration and temperature between a CO₂-enriched and control greenhouse. We cultivated Alstroemeria 'Hanhera' in the two greenhouses and assessed the growth parameters (stem length, stem thickness, and the number of flowers) and yield. The CO₂-enriched greenhouse had a CO₂ generator that produced CO₂ at rate of 0.36 kg/h and its windows were programmed to open when the temperature exceeded 20℃ and close when it dropped below 15℃. The control greenhouse had no additional CO₂ supplementation, and its windows were programmed to open when the temperature exceeded 20℃ and close at approximately 17:00. In the morning, CO₂ concentration remained above 500 ppm in the CO₂-enriched greenhouse, which was higher than that in the control greenhouse (approximately 370 ppm). The ventilation effect only through the side windows to reduce the temperature in both greenhouses did not appear dynamically. CO₂ supplementation promoted plant growth, resulting in a significant increase in plant yield of over 60% compared to that of the control greenhouse. Our findings suggest that elevated CO₂ concentration in the morning can significantly promote the growth and development of Alstroemeria during the winter.

• Journal of Electrochemical Science and Technology
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• v.11 no.2
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• pp.187-194
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• 2020

Two types of sodium cobalt pyrophosphates, triclinic Na_3.12Co_2.44(P₂O₇)₂ and orthorhombic Na₂CoP₂O₇, are compared as high-voltage cathode materials for Na-ion batteries. Na₂CoP₂O₇ shows no electrochemical activity, delivering negligible capacity. In contrast, Na_3.12Co_2.44(P₂O₇)₂ exhibits good electrochemical performance, such as high redox potential at ca. 4.3 V (vs. Na/Na⁺) and stable capacity retention over 50 cycles, although Na_3.12Co_2.44(P₂O₇)₂ delivered approximately 40 mA h g^-1. This is attributed to the fact that Na₂CoP₂O₇ (~3.1 Å) has smaller diffusion channel size than Na_3.12Co_2.44(P₂O₇)₂ (~4.2 Å). Moreover, the electrochemical performance of Na_3.12Co_2.44(P₂O₇)₂ is examined using Na cells and Li cells. The overpotential of Na cells is smaller than that of Li cells. This is due to the fact that Na_3.12Co_2.44(P₂O₇)₂ has a smaller charge transfer resistance and higher diffusivity for Na⁺ ions than Li⁺ ions. This implies that the large channel size of Na_3.12Co_2.44(P₂O₇)₂ is more appropriate for Na⁺ ions than Li⁺ ions. Therefore, Na_3.12Co_2.44(P₂O₇)₂ is considered a promising high-voltage cathode material for Na-ion batteries, if new electrolytes, which are stable above 4.5 V vs. Na/Na⁺, are introduced.

• Journal of the Korean Wood Science and Technology
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• v.48 no.6
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• pp.847-860
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• 2020

This study was conducted into combustion characteristics and gases generated by the combustion of charcoal and agglomerated charcoal distributed in the domestic using a combustion chamber based on the average space per crater of a charcoal-grilled restaurant in South Korea. Each of the three types of charcoals and agglomerated wood charcoals was analyzed for fuel and combustion characteristics. In addition, the concentration changes of CO, CO₂, NO_x, and O₂ were measured for 20 minutes depending on ventilation. As a result, CO yield without ventilation was measured in the range of 1390 to 4703 ppm, and CO yield with ventilation decreases about 29.8% to 57.4%. CO₂ yield without ventilation was measured in the range of 1.34% to 2.42%, and CO₂ yield was about 44.1% to 53.6% when the emission was more than about 1.5% at 10 minutes. The NOx yield was divided into two cases where the NO_x yield was continuously increased because of incomplete combustion, emitted ranging from 29 ppm to 47 ppm, and where emission was constant after 1 minute in the range of 9 ppm to 18 ppm. The NO_x yield with ventilation tends to be similar to the without ventilation, and NO_x yield decreases up to 62.5%. Therefore, it could be used for health risk assessment with the simulation of the usage environment of charcoal and agglomerated wood charcoal.

• Journal of Environmental Science International
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• v.33 no.6
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• pp.355-365
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• 2024

This study was conducted to investigate the effects of CO₂ supplement on growth and quality in greenhouse lettuce cultivation. When CO₂ was supplied at 1,500 ppm in lettuce cultivation, overall growth parameters such as number of leaves, leaf area, plant length, fresh weight, and dry weight were superior compared to those of the control group. While there was no significant difference in relative growth rate due to CO₂ supplement, an increase in leaf area index was observed with CO₂ usage. Furthermore, although there was no significant difference in the content of water-soluble vitamins such as Vitamin C, B1, B2, B5, and B6 due to CO₂ supplement, the Vitamin B3 content in the CO₂ treatment group was 0.5 mg/kg higher than in the control group. Therefore, the use of CO₂ in lettuce cultivation resulted in increased yield and promoted growth, enabling early harvesting.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.5
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• pp.118-127
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• 2021

Recently, the public's interest in the air environment has increased, and public health is threatened by fine particulate matter. Furthermore, the government continues efforts to improve air quality by expanding the monitoring of air pollutants and reinforcing environmental standards. Since air quality differs depending on the region in the Korean Peninsula, it is currently necessary to identify the cause and search for influencing factors. In this study, the atmospheric environment and regional differences in cities located in the Chungnam Province were observed. As a research method, regression analysis was performed for weather conditions, such as temperature, wind speed, precipitation, and season and targeted at air pollutants, such as SO₂, NO₂, CO, O₃, PM₁₀, and PM_2.5, as well as heavy metals contained in particulate matter, such as Pb, Cd, Cr, Cu, Ni, As, Mn, Fe, Al, Ca, and Mg. In the case of PM₁₀, the concentrations of Mn(0.4884) in Cheonan, CO(0.3329) in Dangjin, and Mg(0.5691) in Seosan were highest. In the case of PM_2.5, Cheonan NO₂(0.4759), Dangjin CO(0.4128), and Seosan NO₂(0.3715) were significantly affected. In summary, the influencing factors vary according to the region in Chungnam province in terms of air quality, and there is a difference in the degree of contribution. Therefore, it is considered that the Korean government's management of air quality is required for each region.

• Journal of the Korean Electrochemical Society
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• v.23 no.4
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• pp.97-104
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• 2020

One of the main challenges of electrochemical water splitting technology is to develop a high performance, low cost oxygen-evolving electrode capable of substituting a noble metal catalyst, Ir or Ru based catalyst. In this work, CoFe₂O₄ nanoparticles with sub-44 nmsize of a inverse spinel structure for oxygen evolution reaction (OER) were synthesized by the injection of KNO₃ and NaOH solution to a preheated CoSO₄ and Fe(NO₃)₃ solution. The synthesis time of CoFe₂O₄ nanoparticles was controlled to control particle and crystallite size. When the synthesis time was 6 h, CoFe₂O₄ nanoparticles had high conductivity and electrochemical surface area. The overpotential at current denstiy of 10 mA/㎠ and Tafel slope of CoFe₂O₄ (6h) were 395 mV and 52 mV/dec, respectively. In addition, the catalyst showed excellent durability for 18 hours at 10 mA/㎠.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.26 no.2
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• pp.105-112
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• 2020

As sprout vegetables of interest growing, its maintaining the quality of the technology was needed to solve the problem of increasing growth and maintain quality after harvest. This experiment proved that the quality of radish sprout vegetable was affected by CO₂ treatment during cultivation. Thus, the effect of CO₂ treatment during cultivation on postharvest quality of radish sprout vegetable was investigated in terms of the quality changes in weight loss, gas partial pressure, SPAD, hue angle external appearance during storage at polypropylene film (thickness 30 ㎛) at 10℃. CO₂ treatment used the way to gas with 700 ppm or carbonated water with 700 ppm and 1,400 ppm. The study revealed that growths on CO₂ treated plant were more than those of non-treatment on stem length. After harvesting, the CO₂ treated plant and control growing little different characteristics on fresh weight, plant length and so on. However, there were no differences between the CO₂ treated plant and control on the Fv/Fm and SOD (superoxide dismutase). In gas partial pressure, the O₂ consumption and CO₂ accumulation of the CO₂ treated plant tended to be more than that of non-treated plant. This study also checked that after packaging, the effects of CO₂ treatment during cultivation on the quality of radish sprout vegetable was not significant. However, there were tended to CO₂ treatments were lower value compared to control on SPAD, hue angle and general appearance. CO₂ treatments of radish sprouting vegetable before harvest were improve growth of stem length, but ones were not improving the maintain of quality on radish sprout vegetable during shelf-life period. The results indicated that CO₂ treatment only affected stem elongation until radish sprout vegetable its growth.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.11a
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• pp.23-24
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• 2014

Currently, cement and concrete industries have been contributing to the CO₂ emission worldwide. Because of that, the efforts to minimize CO₂ have been the subject of many researches. This study focus on the use of GGBFS and fly ash in mortar specimens as a patial replacement of cement. Because of the limitation of the initial compressive strength, the newly efforts to enhance the strength through CO₂ Curing was adapted. To accelerate the reaction with CO₂, MgO was replaced by percentage from 0 to 100%. Results showed that compressive strength values at 7 days with CO₂ curing done on specimens was higher than that with no CO₂ curing. Similar trend was observed at 14 days too. It is therefore appeared that CO₂ curing has an obvious effect on compressive strength development of mortar specimens.